Thursday, November 14, 2013

New paper finds a significant decreased temperature trend in China during 20th century

A new paper published in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs May-July maximum temperatures in China over the past 267 years and finds that there was a significant decrease in temperatures over the 20th century. According to the authors, the "Reconstruction exhibits a significant decreased trend in 20th century" and "The reconstructed [temperatures are] similar to several observed [temperature series] and the temperature index in north-central China, which indicated that the decrease in summer temperatures in the 20th century was a large scale phenomenon."

Abstract

A tree–ring–width chronology of Pinus tabulaeformis was developed from the Qianshan Mountain, Liaoning province, northeastern China. Based on the correlation between the ring width and instrumental data, a transfer function was designed and the May–July mean maximum temperature (MMT) from 1745 to 2012 was reconstructed. The reconstruction explains 42.7% of the instrumental variance during the calibration period (41.7% after adjusting for the loss of the degrees of freedom). The reconstructed MMT is similar to several observed MMT series and the temperature index in north-central China, which indicated that the decrease in summer temperatures in the 20th century was a large scale phenomenon. The reconstruction also showed that high MMT values corresponded to historical drought events in Liaoning. In addition, a spatial correlation analyses revealed that the MMT reconstruction is regionally representative. Significant 128.2-, 64.1-, 18.6-, 3.46-, 3.19-, 2.43-, 2.15- and 2.10-year cycles were detected in the reconstructed MMT series from Qianshan Mountain.